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<title>safe_signed_literal<Value, PP , EP> and safe_unsigned_literal<Value, PP, EP></title>
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<td valign="top"><img href="index.html" height="164px" src="pre-boost.jpg" alt="Library Documentation Index"></td>
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<td><h2>Safe Numerics</h2></td>
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<a accesskey="p" href="safe_range.html"><img src="images/prev.png" alt="Prev"></a><a accesskey="u" href="types.html"><img src="images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="images/home.png" alt="Home"></a><a accesskey="n" href="exception.html"><img src="images/next.png" alt="Next"></a>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="safe_numerics.safe_literal"></a>safe_signed_literal<Value, PP , EP> and
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safe_unsigned_literal<Value, PP, EP></h3></div></div></div>
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<div class="toc"><dl class="toc">
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<dt><span class="section"><a href="safe_literal.html#idm130203096240">Description</a></span></dt>
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<dt><span class="section"><a href="safe_literal.html#idm130203094736">Model of</a></span></dt>
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<dt><span class="section"><a href="safe_literal.html#idm130203090832">Associated Types</a></span></dt>
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<dt><span class="section"><a href="safe_literal.html#idm130203083840">Template Parameters</a></span></dt>
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<dt><span class="section"><a href="safe_literal.html#idm130203066304">Inherited Valid Expressions</a></span></dt>
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<dt><span class="section"><a href="safe_literal.html#idm130203034032">Example of use</a></span></dt>
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<dt><span class="section"><a href="safe_literal.html#safe_numerics.safe_literal.make_safe_literal"><code class="computeroutput">make_safe_literal(n, PP, EP) </code></a></span></dt>
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<dt><span class="section"><a href="safe_literal.html#idm130203017088">Header</a></span></dt>
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</dl></div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="idm130203096240"></a>Description</h4></div></div></div>
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<p>A safe type which holds a literal value. This is required to be able
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to initialize other safe types in such a way that an exception code is not
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generated. It is also useful when creating constexpr versions of safe
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types. It contains one immutable value known at compile time and hence can
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be used in any constexpr expression.</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="idm130203094736"></a>Model of</h4></div></div></div>
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<p><a class="link" href="numeric.html" title="Numeric<T>">Integer</a></p>
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<p><a class="link" href="safe_numeric_concept.html" title="SafeNumeric<T>">SafeNumeric</a></p>
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<p>This type inherits all the notation, associated types and template
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parameters and valid expressions of <a class="link" href="safe_numeric_concept.html" title="SafeNumeric<T>">SafeNumeric</a> types. The
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following specify additional features of this type.</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="idm130203090832"></a>Associated Types</h4></div></div></div>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col align="left">
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<col align="left">
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</colgroup>
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<tbody>
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<tr>
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<td align="left"><code class="computeroutput">PP</code></td>
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<td align="left">A type which specifies the result type of an expression
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using safe types.</td>
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</tr>
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<tr>
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<td align="left"><code class="computeroutput">EP</code></td>
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<td align="left">A type containing members which are called when a correct
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result cannot be returned</td>
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</tr>
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</tbody>
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</table></div>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="idm130203083840"></a>Template Parameters</h4></div></div></div>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col align="left">
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<col align="left">
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<col align="left">
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</colgroup>
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<thead><tr>
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<th align="left">Parameter</th>
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<th align="left">Type Requirements</th>
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<th align="left">Description</th>
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</tr></thead>
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<tbody>
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<tr>
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<td align="left"><code class="computeroutput">Value</code></td>
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<td align="left"><code class="computeroutput"><a class="link" href="numeric.html" title="Numeric<T>">Integer</a></code></td>
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<td align="left">value used to initialize the literal</td>
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</tr>
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<tr>
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<td align="left"><code class="computeroutput">PP</code></td>
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<td align="left"><a class="link" href="numeric.html" title="Numeric<T>">PromotionPolicy<PP></a></td>
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<td align="left"><p>Optional promotion policy. Default value is
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<code class="computeroutput">void</code></p></td>
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</tr>
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<tr>
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<td align="left"><code class="computeroutput">EP</code></td>
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<td align="left"><a class="link" href="numeric.html" title="Numeric<T>">Exception
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Policy<EP></a></td>
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<td align="left"><p>Optional exception policy. Default value is
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<code class="computeroutput">void</code></p></td>
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</tr>
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</tbody>
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</table></div>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="idm130203066304"></a>Inherited Valid Expressions</h4></div></div></div>
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<p>safe literal types are immutable. Hence they only inherit those
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valid expressions which don't change the value. <span class="emphasis"><em>This excludes
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assignment, increment, and decrement and all unary operators except unary
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-, + and ~</em></span>. Other than that, they can be used anywhere a <a class="link" href="safe_numeric_concept.html" title="SafeNumeric<T>">SafeNumeric</a> type can
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be used. Note that the default promotion and exception policies are void.
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This is usually convenient since when a safe literal is used in a binary
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operation, this will inherit the policies of the other type. On the other
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hand, this can be inconvenient when operands of a binary expression are
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both safe literals. This will fail to compile since there are no
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designated promotion and exception policies. The way to address this to
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assign specific policies as in this example.</p>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span>
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<span class="keyword">using</span> <span class="identifier">compile_time_value</span> <span class="special">=</span> <span class="identifier">safe_signed_literal</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span><span class="special">;</span>
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<span class="keyword">constexpr</span> <span class="identifier">compile_time_value</span><span class="special"><</span><span class="number">1000</span><span class="special">></span> <span class="identifier">x</span><span class="special">;</span>
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<span class="keyword">constexpr</span> <span class="identifier">compile_time_value</span><span class="special"><</span><span class="number">0</span><span class="special">></span> <span class="identifier">y</span><span class="special">;</span>
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<span class="comment">// should compile and execute without problem</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">x</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span>
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<span class="comment">// all the following statements should fail to compile because there are </span>
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<span class="comment">// no promotion and exception policies specified.</span>
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<span class="keyword">constexpr</span> <span class="identifier">safe</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">z</span> <span class="special">=</span> <span class="identifier">x</span> <span class="special">/</span> <span class="identifier">y</span><span class="special">;</span>
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</pre>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="idm130203034032"></a>Example of use</h4></div></div></div>
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<pre class="programlisting"><a href="../../include/safe_integer_literal.hpp" target="_top"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">numeric</span><span class="special">/</span><span class="identifier">safe_numerics</span><span class="special">/</span><span class="identifier">safe_integer_literal</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></a>
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<span class="keyword">constexpr</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">safe_signed_literal</span><span class="special"><</span><span class="number">42</span><span class="special">></span> <span class="identifier">x</span><span class="special">;</span>
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</pre>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="safe_numerics.safe_literal.make_safe_literal"></a><code class="computeroutput">make_safe_literal(n, PP, EP) </code>
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</h4></div></div></div>
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<p>This is a macro which returns an instance of a safe literal type.
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This instance will hold the value n. The type of the value returned will
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be the smallest safe type which can hold the value <code class="computeroutput">n</code>.</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="idm130203017088"></a>Header</h4></div></div></div>
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<p><a href="../../include/safe_integer_literal.hpp" target="_top">#include
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<boost/numeric/safe_numerics/safe_integer_literal.hpp></a></p>
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</div>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2012-2018 Robert Ramey<p><a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">Subject to Boost
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Software License</a></p>
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</div></td>
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</tr></table>
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<hr>
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